1. Field of the Invention
The present invention relates to novel urethanes and to the methods of making and using same. More specifically, the present invention relates to novel urethanes which can be derived from isocyanates.
2. Brief Description of the Prior Art
Curable compositions containing blocked isocyanate crosslinking agents are known in the art. Some of the crosslinking agents aid in effecting cure of these compositions at relatively low temperatures of about 320.degree.-350.degree. F. (160.degree.-177.degree. C.) over a period of 20 to 30 minutes. Yet, lower temperature cure is required for coated substrates which have plastic parts which tend to deform at the afore-stated temperatures. Hence, much work has been done to formulate compositions that cure effectively at relatively lower temperatures.
As is the case here, much work has been done in developing blocked isocyanate crosslinking agents which would aid in effecting cure at lower temperatures. The work done has shown that proper selection of blocking agents for isocyanate groups is determinative in effecting cure at low temperatures. It is believed that blocked isocyanates that unblock readily at low temperatures effect cure of coatings at low temperatures. However, their use in coating compositions is limited in some respects. In one respect, coatings derived therefrom, although useful, may have poor solvent resistance, indicating a relatively low degree of cure. In another respect, the coatings, although more completely cured, may have poor appearance. In yet another respect, some of these coating compositions, particularly the water-based compositions, are rather unstable.
By the present invention, a select group of blocking agents which are superior to blocking agents of the prior art have been found effective in overcoming the afore-stated limitations.